Heating Ventilating and Air Conditioning: Analysis and Design
6th Edition
ISBN: 9780471470151
Author: Faye C. McQuiston, Jeffrey D. Spitler, Jerald D. Parker
Publisher: Wiley, John & Sons, Incorporated
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Chapter 5, Problem 5.28P
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One vessel having a carbon-steel wall of thickness 5 mm
carrying
saturated steam and water at 423K. The vessel is insulated with magnesia of
thickness 50 mm. If the ambient air temperature is 321 K, determine the heat
loss from the vessel.
Given:
i. thermal conductivity of carbon steel is 52 W/m.K
ii. thermal conductivity of magnesia is 0.5 W/m.K
iii. surface coefficient of insulation surface is 3 W/m2.K
2) Urethane (k = 0.026 W/m-K) is used to insulate the sidewall and the top and bottom of a cylindrical
hot water tank. The insulation is 40 mm thick and is sandwiched between sheet metal of thin-wall
construction. The height and inside diameter of the tank are 2 m and 0.8 m, respectively. The tank is in
ambient air with T = 10 °C and h = 10 W/m²-K. If the hot water maintains the inner surface at 55 °C, and
energy costs amount to $0.15 per kWh, what is the daily cost to maintain the water in storage? Argue
that the thermal resistance of the tank wall is negligible. What does this say about the temperature drop
across the tank wall?
Consider a long, insulated cable supplying power to a community. It is elevated in the air by using poles. The ambient air temperature is 20oC and the convective heat transfer coefficient is h = 20 W/m2.K. Radiation exchange between the cable surface and the environment can be neglected. Make your calculations considering per meter-length. The wire carries 500 Amp current and has a resistance of 0.0001 Ohm/m. The diameter of the solid core wire is 1.0 cm and has a thermal conductivity of k = 20 W/m.K The electrically insulating material covering the wire-core has a thickness of 0.5 cm with a thermal conductivity of k = 0.01 W/m.K
a) What is the rate of heat loss from the cable to the environment in kW/meter?
b) What is the outside surface (exposed to air) temperature of the cable?
c) What is the temperature of the interface between the insulation sleeve and the core-wire carrying the electric power? If the sleeve material has to remain below 100 oC for the long term, would this…
Chapter 5 Solutions
Heating Ventilating and Air Conditioning: Analysis and Design
Ch. 5 - Determine the thermal conductivity of 4 in. (100...Ch. 5 - Compute the unit conductance C for 512 in. (140...Ch. 5 - Compute the unit thermal resistance and the...Ch. 5 - What is the unit thermal resistance for an inside...Ch. 5 - Compute the thermal resistance per unit length for...Ch. 5 - Assuming that the blocks are not filled, compute...Ch. 5 - The partition of Problem 5-4 has still air on one...Ch. 5 - The pipe of Problem has water flowing inside with...Ch. 5 - Compute the overall thermal resistance of a wall...Ch. 5 - Compute the overall heat-transfer coefficient for...
Ch. 5 - Estimate what fraction of the heat transfer for a...Ch. 5 - Make a table similar to Table 5-4a showing...Ch. 5 - Estimate the unit thermal resistance for a...Ch. 5 - Refer to Problem 5-13, and estimate the unit...Ch. 5 - A ceiling space is formed by a large flat roof and...Ch. 5 - A wall is 20 ft (6.1 m) wide and 8 ft (2.4 m) high...Ch. 5 - Estimate the heat-transfer rate per square foot...Ch. 5 - A wall exactly like the one described in Table...Ch. 5 - Prob. 5.19PCh. 5 - Compute the overall heat-transfer coefficient for...Ch. 5 - Compute the overall heat transfer for a single...Ch. 5 - Determine the overall heattransfer coefficient for...Ch. 5 - A basement is 2020ft(66m) and 7 ft (2.13 m) below...Ch. 5 - Estimate the overall heat-transfer coefficient for...Ch. 5 - Rework Problem 5-23 assuming that the walls are...Ch. 5 - A heated building is built on a concrete slab with...Ch. 5 - A basement wall extends 6 ft (1.8 m) below grade...Ch. 5 - A 2440ft(7.312.2m) building has a full basement...Ch. 5 - The floor of the basement described in Problem...Ch. 5 - Assume that the ground temperature tg is 40 F (10...Ch. 5 - Use the temperatures given in Problem 5-30 and...Ch. 5 - A small office building is constructed with a...Ch. 5 - A 100 ft length of buried, uninsulated steel pipe...Ch. 5 - Estimate the heat loss from 100 m of buried...Ch. 5 - A large beverage cooler resembles a small building...Ch. 5 - Consider the wall section shown in Fig. 5-10. (a)...Ch. 5 - A building has floor plan dimensions of 3060ft....Ch. 5 - Compute the temperature of the metal roof deck of...Ch. 5 - Consider the wall section shown in Fig. -4a,...Ch. 5 - Consider the knee space shown in Fig. 5-11. The...Ch. 5 - Estimate the temperature in an unheated basement...
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